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Perinatal expansion of pancreatic β cells is critical to metabolic adaptation. Yet, mechanisms surveying the fidelity by which proliferative events generate functional β cell pools remain unknown. We have previously identified a CCR2 + myeloid niche required for peri-natal β cell replication, with β cells dynamically responding to loss and repopulation of these myeloid cells with growth arrest and rebound expansion, respectively. Here, using a timed single-cell RNA-sequencing approach, we show that transient disruption of perinatal CCR2 + macrophages change islet β cell repertoires in young mice to resemble those of aged mice. Gene expression profiling and functional assays disclose prominent mitochondrial defects in β cells coupled to impaired redox states, NAD depletion, and DNA damage, leading to accelerated islets' dysfunction with age. These findings reveal an unexpected vulnerability of mitochondrial β cells' bioenergetics to the disruption of perinatal CCR2 + macrophages, implicating these cells in surveying early in life both the size and energy homeostasis of β cells populations., Competing Interests: The authors declare no competing interest.

Since 2007 financial recovery plans have been adopted by some Italian regions to contain the costs of the healthcare sector. It is legitimate to ask whether spending cuts associated with the austerity policy have had any effect on the health of the citizens. We examine the indirect impact of financial recovery plans on a broad set of health indicators, accounting for several dimensions of both physical and psychological diseases. We use an instrumental variable fixed-effects model to control for time-varying heterogeneity and to deal with the potential endogeneity of the enrolment in the austerity programme. We find that the Italian austerity policy Piano di Rientro resulted in unintended negative effects on several dimensions of health, hurting and potentially jeopardising the health of citizens., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

In their recent Cell Reports paper, Chang and colleagues report on a successful strategy to achieve durable mixed hematopoietic chimerism that promotes the engraftment and long-term function of pancreatic islet allotransplants in fully immunocompetent mice without immunosuppression., Competing Interests: Declaration of interests The authors declare no competing interests., (Published by Elsevier Inc.)

Functional implication of stromal heterogeneity in the prostate remains incompletely understood. Using lineage tracing and light-sheet imaging, we show that some fibroblast cells at the mouse proximal prostatic ducts and prostatic urethra highly express Lgr5. Genetic ablation of these anatomically restricted stromal cells, but not nonselective ablation of prostatic stromal cells, rapidly induces prostate epithelial turnover and dedifferentiation that are reversed following spontaneous restoration of the Lgr5 + stromal cells. RNA sequencing (RNA-seq) analysis indicates that ablating the Lgr5 + stromal cells activates a mechanosensory response. Ablating the Lgr5 + stromal cells impairs the control of prostatic ductal outlet, increases prostate tissue stiffness, and activates the mitogen-activated protein kinase (MAPK). Suppressing MAPK overrides the elevated epithelial proliferation. In summary, the Lgr5 + stromal cells regulate prostate tissue homeostasis and maintain its functional integrity in a long-distance manner. Our study implies that the cells at organ junctions most likely control organ homeostasis by sustaining a balanced mechanoforce., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Many tumors of endodermal origin are composed of highly secretory cancer cells that must adapt endoplasmic reticulum (ER) activity to enable proper folding of secreted proteins and prevent ER stress. We found that pancreatic ductal adenocarcinomas (PDACs) overexpress the myelin regulatory factor (MYRF), an ER membrane-associated transcription factor (TF) released by self-cleavage. MYRF was expressed in the well-differentiated secretory cancer cells, but not in the poorly differentiated quasi-mesenchymal cells that coexist in the same tumor. MYRF expression was controlled by the epithelial identity TF HNF1B, and it acted to fine-tune the expression of genes encoding highly glycosylated, cysteine-rich secretory proteins, thus preventing ER overload. MYRF-deficient PDAC cells showed signs of ER stress, impaired proliferation, and an inability to form spheroids in vitro, while in vivo they generated highly secretory but poorly proliferating and hypocellular tumors. These data indicate a role of MYRF in the control of ER homeostasis in highly secretory PDAC cells., Competing Interests: Declaration of Interests The authors declare no conflict of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Objective: Diabetes is characterized by pancreatic β-cell dedifferentiation. Dedifferentiating β cells inappropriately metabolize lipids over carbohydrates and exhibit impaired mitochondrial oxidative phosphorylation. However, the mechanism linking the β-cell's response to an adverse metabolic environment with impaired mitochondrial function remains unclear., Methods: Here we report that the oxidoreductase cytochrome b5 reductase 3 (Cyb5r3) links FoxO1 signaling to β-cell stimulus/secretion coupling by regulating mitochondrial function, reactive oxygen species generation, and nicotinamide actin dysfunction (NAD)/reduced nicotinamide actin dysfunction (NADH) ratios., Results: The expression of Cyb5r3 is decreased in FoxO1-deficient β cells. Mice with β-cell-specific deletion of Cyb5r3 have impaired insulin secretion, resulting in glucose intolerance and diet-induced hyperglycemia. Cyb5r3-deficient β cells have a blunted respiratory response to glucose and display extensive mitochondrial and secretory granule abnormalities, consistent with altered differentiation. Moreover, FoxO1 is unable to maintain expression of key differentiation markers in Cyb5r3-deficient β cells, suggesting that Cyb5r3 is required for FoxO1-dependent lineage stability., Conclusions: The findings highlight a pathway linking FoxO1 to mitochondrial dysfunction that can mediate β-cell failure., (Copyright © 2020 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

Efficient stem cell differentiation into pancreatic islet cells is of critical importance for the development of cell replacement therapies for diabetes. Here, we identify the expression pattern of connexin 43 (Cx43), a gap junction (GJ) channel protein, in human embryonic stem cell (hESC)-derived definitive endoderm (DE) and primitive gut tube cells, representing early lineages for posterior foregut (PF), pancreatic progenitors (PP), pancreatic endocrine progenitors (PE), and islet cells. As the function of GJ channels is dependent on their gating status, we tested the impact of supplementing hESC-derived PP cell cultures with AAP10, a peptide that promotes Cx43 GJ channel opening. We found that this treatment promotes the expression of DE markers FoxA2 and Sox17, leads to a more efficient derivation of DE, and improves the yield of PF, PP, and PE cells. These results demonstrate a functional involvement of GJ channels in the differentiation of embryonic stem cells into pancreatic cell lineages., (Copyright © 2019. Published by Elsevier Inc.)

Many theories have been advanced to better understand why β cell function and structure relentlessly deteriorate during the course of type 2 diabetes (T2D). These theories include inflammation, apoptosis, replication, neogenesis, autophagy, differentiation, dedifferentiation, and decreased levels of insulin gene regulatory proteins. However, none of these have considered the possibility that endogenous self-repair of existing β cells may be an important factor. To examine this hypothesis, we conducted studies with female Zucker diabetic fatty rats fed a high-fat diet (HFD) for 1, 2, 4, 7, 9, 18, or 28 days, followed by a return to regular chow for 2-3 weeks. Repair was defined as reversal of elevated blood glucose and of inappropriately low blood insulin levels caused by a HFD, as well as reversal of structural damage visualized by imaging studies. We observed evidence of functional β cell damage after a 9-day exposure to a HFD and then repair after 2-3 weeks of being returned to normal chow (blood glucose [BG] = 348 ± 30 vs. 126 ± 3; mg/dl; days 9 vs. 23 day, P < 0.01). After 18- and 28-day exposure to a HFD, damage was more severe and repair was less evident. Insulin levels progressively diminished with 9-day exposure to a HFD; after returning to a regular diet, insulin levels rebounded toward, but did not reach, normal values. Increase in β cell mass was 4-fold after 9 days and 3-fold after 18 days, and there was no increase after 28 days of a HFD. Increases in β cell mass during a HFD were not different when comparing values before and after a return to regular diet within the 9-, 18-, or 28-day studies. No changes were observed in apoptosis or β cell replication. Formation of intracellular markers of oxidative stress, intranuclear translocation of Nrf2, and formation of intracellular antioxidant proteins indicated the participation of HFD/oxidative stress induction of the Nrf2/antioxidant pathway. Flow cytometry-based assessment of β cell volume, morphology, and insulin-specific immunoreactivity, as well as ultrastructural analysis by transmission electron microscopy, revealed that short-term exposure to a HFD produced significant changes in β cell morphology and function that are reversible after returning to regular chow. These results suggest that a possible mechanism mediating the ability of β cells to self-repair after a short-term exposure to a HFD is the activation of the Nrf2/antioxidant pathway.

The development and function of epithelia depend on the establishment and maintenance of cell-cell adhesion and intercellular junctions, which operate as mechanosensor hubs for the transduction of biochemical signals regulating cell proliferation, differentiation, survival, and regeneration. Here, we show that αE-catenin, a key component of adherens junctions, functions as a positive regulator of pancreatic islet cell lineage differentiation by repressing the sonic hedgehog pathway (SHH). Thus, deletion of αE-catenin in multipotent pancreatic progenitors resulted in (1) loss of adherens junctions, (2) constitutive activation of SHH, (3) decrease in islet cell lineage differentiation, and (4) accumulation of immature Sox9 + progenitors. Pharmacological blockade of SHH signaling in pancreatic organ cultures and in vivo rescued this defect, allowing αE-catenin-null Sox9 + pancreatic progenitors to differentiate into endocrine cells. The results uncover crucial functions of αE-catenin in pancreatic islet development and harbor significant implications for the design of β cell replacement and regeneration therapies in diabetes., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Organ-specific patterns of myeloid cells may contribute tissue-specific growth and/or regenerative potentials. The perinatal stage of pancreas development marks a time characterized by maximal proliferation of pancreatic islets, ensuring the maintenance of glucose homeostasis throughout life. Ontogenically distinct CX3CR1+ and CCR2+ macrophage populations have been reported in the adult pancreas, but their functional contribution to islet cell growth at birth remains unknown. Here, we uncovered a temporally restricted requirement for CCR2+ myeloid cells in the perinatal proliferation of the endocrine pancreatic epithelium. CCR2+ macrophages are transiently enriched over CX3CR1+ subsets in the neonatal pancreas through both local expansion and recruitment of immature precursors. Using CCR2-specific depletion models, we show that loss of this myeloid population leads to a striking reduction in β cell proliferation, dysfunctional islet phenotypes, and glucose intolerance in newborns. Replenishment of pancreatic CCR2+ myeloid compartments by adoptive transfer rescues these defects. Gene profiling identifies pancreatic CCR2+ myeloid cells as a prominent source of IGF2, which contributes to IGF1R-mediated islet proliferation. These findings uncover proproliferative functions of CCR2+ myeloid subsets and identify myeloid-dependent regulation of IGF signaling as a local cue supporting pancreatic proliferation.

Loss of β cell identity, the presence of polyhormonal cells, and reprogramming are emerging as important features of β cell dysfunction in patients with type 1 and type 2 diabetes. In this study, we have demonstrated that the transcription factor NKX2.2 is essential for the active maintenance of adult β cell identity as well as function. Deletion of Nkx2.2 in β cells caused rapid onset of a diabetic phenotype in mice that was attributed to loss of insulin and downregulation of many β cell functional genes. Concomitantly, NKX2.2-deficient murine β cells acquired non-β cell endocrine features, resulting in populations of completely reprogrammed cells and bihormonal cells that displayed hybrid endocrine cell morphological characteristics. Molecular analysis in mouse and human islets revealed that NKX2.2 is a conserved master regulatory protein that controls the acquisition and maintenance of a functional, monohormonal β cell identity by directly activating critical β cell genes and actively repressing genes that specify the alternative islet endocrine cell lineages. This study demonstrates the highly volatile nature of the β cell, indicating that acquiring and sustaining β cell identity and function requires not only active maintaining of the expression of genes involved in β cell function, but also continual repression of closely related endocrine gene programs., Competing Interests: The authors have declared that no conflict of interest exists.

Functional characterization of individual cells within heterogeneous tissue preparations is challenging. Here, we report the development of a versatile imaging method that assesses single cell responses of various endpoints in real time, while identifying the individual cell types. Endpoints that can be measured include (but are not limited to) ionic flux (calcium, sodium, potassium and hydrogen), metabolic responsiveness (NAD(P)H, mitochondrial membrane potential), and signal transduction (H 2 O 2 and cAMP). Subsequent to fluorescent imaging, identification of cell types using immunohistochemistry allows for mapping of cell type to their respective functional real time responses. To validate the utility of this method, NAD(P)H responses to glucose of islet alpha versus beta cells generated from dispersed pancreatic islets, followed by the construction of frequency distributions characterizing the variability in the magnitude of each individual cell responses were compared. As expected, no overlap between the glucose response frequency distributions for beta cells versus alpha cells was observed, thereby establishing both the high degree of fidelity and low rate of both false-negatives and false-positives in this approach. This novel method has the ability not only to resolve single cell level functional differences between cell types, but also to characterize functional heterogeneity within a given cell type.

Fibrotic disorders involve replacement of normal parenchyma with myofibroblasts, which deposit connective tissue, leading to obliteration of the function of the underlying organ. The treatment options are inadequate and reflect the fact that signaling targets in myofibroblasts are unknown. Here we identify the hyperactive Lyn signaling in myofibroblasts of patients with chronic pancreatitis-induced fibrosis. Lyn activation coexpress with markers of activated myofibroblasts, and is increased ~11-fold in chronic pancreatitis compared to normal tissue. Inhibition of Lyn with siRNA or INNO-406 leads to the substantial decrease of migration and proliferation of human chronic pancreatitis myofibroblasts in vitro, while leaving migration and proliferation of normal myofibroblasts only slightly affected. Furthermore, inhibition of Lyn prevents synthesis of procollagen and collagen in myofibroblasts in a mouse model of chronic pancreatitis-induced fibrosis. We conclude that Lyn, as a positive regulator of myofibroblast migration, proliferation, and collagen production, is a key target for preventing fibrosis.

During pancreas development, epithelial buds undergo branching morphogenesis to form an exocrine and endocrine gland. Proper morphogenesis is necessary for correct lineage allocation of pancreatic progenitors; however, the cellular events underlying pancreas morphogenesis are unknown. Here, we employed time-lapse microscopy and fluorescent labeling of cells to analyze cell behaviors associated with pancreas morphogenesis. We observed that outer bud cells adjacent to the basement membrane are pleomorphic and rearrange frequently; additionally, they largely remain in the outer cell compartment even after mitosis. These cell behaviors and pancreas branching depend on cell contacts with the basement membrane, which induce actomyosin cytoskeleton remodeling via integrin-mediated activation of FAK/Src signaling. We show that integrin signaling reduces E-cadherin-mediated cell-cell adhesion in outer cells and provide genetic evidence that this regulation is necessary for initiation of branching. Our study suggests that regulation of cell motility and adhesion by local niche cues initiates pancreas branching morphogenesis., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)

Our previous work demonstrated an important role of EpCAM in the regulation of pancreatic cell adhesion, growth and differentiation. Here we investigated the consequences of human EpCAM (hEpCAM) overexpression under the control of the MMTV-LTR promoter, known to drive robust gene expression in a number of ductal epithelia, including the pancreas. In this animal model (MMTV-hEpCAM) we uncovered a striking pancreatic phenotype exhibiting a 12-fold increase in the islet cell mass, with normal expression patterns of insulin and the transcription factor PDX-1. Intriguingly, these large islet clusters revealed an altered architectural organization of α- and δ-cells that appeared interspersed with β-cells in the islet cores. This suggests an effect of the hEpCAM transgene on the function of other cell adhesion molecules that we have previously shown to regulate islet cell type segregation. Consistent with this finding, we show that the pancreatic epithelium in MMTV-hEpCAM transgenic mice exhibits a redistribution of β-catenin, a known regulator of E-cadherin-mediated adhesions. Collectively, these results provide an important in vivo validation of hEpCAM signaling properties in normal epithelia and offer unique opportunities to further explore the function of this glycoprotein in select pancreatic cell lineages to elicit islet cell expansion, and/or regeneration in diabetes., (© The Author(s) 2015.)

Directed differentiation of human pluripotent stem cells into functional insulin-producing beta-like cells holds great promise for cell replacement therapy for patients suffering from diabetes. This approach also offers the unique opportunity to study otherwise inaccessible aspects of human beta cell development and function in vitro. Here, we show that current pancreatic progenitor differentiation protocols promote precocious endocrine commitment, ultimately resulting in the generation of non-functional polyhormonal cells. Omission of commonly used BMP inhibitors during pancreatic specification prevents precocious endocrine formation while treatment with retinoic acid followed by combined EGF/KGF efficiently generates both PDX1(+) and subsequent PDX1(+)/NKX6.1(+) pancreatic progenitor populations, respectively. Precise temporal activation of endocrine differentiation in PDX1(+)/NKX6.1(+) progenitors produces glucose-responsive beta-like cells in vitro that exhibit key features of bona fide human beta cells, remain functional after short-term transplantation, and reduce blood glucose levels in diabetic mice. Thus, our simplified and scalable system accurately recapitulates key steps of human pancreas development and provides a fast and reproducible supply of functional human beta-like cells., (© 2015 The Authors.)

The naïve pluripotent state has been shown in mice to lead to broad and more robust developmental potential relative to primed mouse epiblast cells. The human naïve ES cell state has eluded derivation without the use of transgenes, and forced expression of OCT4, KLF4, and KLF2 allows maintenance of human cells in a naïve state [Hanna J, et al. (2010) Proc Natl Acad Sci USA 107(20):9222-9227]. We describe two routes to generate nontransgenic naïve human ES cells (hESCs). The first is by reverse toggling of preexisting primed hESC lines by preculture in the histone deacetylase inhibitors butyrate and suberoylanilide hydroxamic acid, followed by culture in MEK/ERK and GSK3 inhibitors (2i) with FGF2. The second route is by direct derivation from a human embryo in 2i with FGF2. We show that human naïve cells meet mouse criteria for the naïve state by growth characteristics, antibody labeling profile, gene expression, X-inactivation profile, mitochondrial morphology, microRNA profile and development in the context of teratomas. hESCs can exist in a naïve state without the need for transgenes. Direct derivation is an elusive, but attainable, process, leading to cells at the earliest stage of in vitro pluripotency described for humans. Reverse toggling of primed cells to naïve is efficient and reproducible.

Macrophages populate the mesenchymal compartment of all organs during embryogenesis and have been shown to support tissue organogenesis and regeneration by regulating remodeling of the extracellular microenvironment. Whether this mesenchymal component can also dictate select developmental decisions in epithelia is unknown. Here, using the embryonic pancreatic epithelium as model system, we show that macrophages drive the epithelium to execute two developmentally important choices, i.e. the exit from cell cycle and the acquisition of a migratory phenotype. We demonstrate that these developmental decisions are effectively imparted by macrophages activated toward an M2 fetal-like functional state, and involve modulation of the adhesion receptor NCAM and an uncommon "paired-less" isoform of the transcription factor PAX6 in the epithelium. Over-expression of this PAX6 variant in pancreatic epithelia controls both cell motility and cell cycle progression in a gene-dosage dependent fashion. Importantly, induction of these phenotypes in embryonic pancreatic transplants by M2 macrophages in vivo is associated with an increased frequency of endocrine-committed cells emerging from ductal progenitor pools. These results identify M2 macrophages as key effectors capable of coordinating epithelial cell cycle withdrawal and cell migration, two events critical to pancreatic progenitors' delamination and progression toward their differentiated fates.

SEL1L, a component of the endoplasmic reticulum associated degradation (ERAD) pathway, has been reported to regulate the (i) differentiation of the pancreatic endocrine and exocrine tissue during the second transition of mouse embryonic development, (ii) neural stem cell self-renewal and lineage commitment and (iii) cell cycle progression through regulation of genes related to cell-matrix interaction. Here we show that in the pancreas the expression of SEL1L is developmentally regulated, such that it is readily detected in developing islet cells and in nascent acinar clusters adjacent to basement membranes, and becomes progressively restricted to the islets of Langherans in post-natal life. This peculiar expression pattern and the presence of two inverse RGD motifs in the fibronectin type II domain of SEL1L protein indicate a possible interaction with cell adhesion molecules to regulate islets architecture. Co-immunoprecipitation studies revealed SEL1L and ß1-integrin interaction and, down-modulation of SEL1L in pancreatic ß-cells, negatively influences both cell adhesion on selected matrix components and cell proliferation likely due to altered ERK signaling. Furthermore, the absence of SEL1L protein strongly inhibits glucose-stimulated insulin secretion in isolated mouse pancreatic islets unveiling an important role of SEL1L in insulin trafficking. This phenotype can be rescued by the ectopic expression of the ß1-integrin subunit confirming the close interaction of these two proteins in regulating the cross-talk between extracellular matrix and insulin signalling to create a favourable micro-environment for ß-cell development and function.

Development of the endocrine compartment of the pancreas, as represented by the islets of Langerhans, occurs through a series of highly regulated events encompassing branching of the pancreatic epithelium, delamination and differentiation of islet progenitors from ductal domains, followed by expansion and three-dimensional organization into islet clusters. Cellular interactions with the extracellular matrix (ECM) mediated by receptors of the integrin family are postulated to regulate key functions in these processes. Yet, specific events regulated by these receptors in the developing pancreas remain unknown. Here, we show that ablation of the β1 integrin gene in developing pancreatic β-cells reduces their ability to expand during embryonic life, during the first week of postnatal life, and thereafter. Mice lacking β1 integrin in insulin-producing cells exhibit a dramatic reduction of the number of β-cells to only ∼18% of wild-type levels. Despite the significant reduction in β-cell mass, these mutant mice are not diabetic. A thorough phenotypic analysis of β-cells lacking β1 integrin revealed a normal expression repertoire of β-cell markers, normal architectural organization within islet clusters, and a normal ultrastructure. Global gene expression analysis revealed that ablation of this ECM receptor in β-cells inhibits the expression of genes regulating cell cycle progression. Collectively, our results demonstrate that β1 integrin receptors function as crucial positive regulators of β-cell expansion.

Injection of tumor cells in mice more than 30 years ago resulted in the discovery of an epithelial antigen, later defined as a cell adhesion molecule (EpCAM). Although EpCAM has since evoked significant interest as a target in cancer therapy, mechanistic insights on the functions of this glycoprotein have been emerging only very recently. This may have been caused by the multitude of functions attributed to the glycoprotein, its localization at different subcellular sites and complex posttranslational modifications. Here, we review how EpCAM modifies cell-cell contact adhesion strength and tissue plasticity, and how it regulates cell proliferation and differentiation. Major knowledge derived from human diseases will be highlighted: Mutant EpCAM that is absent from the cell surface leads to fatal intestinal abnormalities (congenital tufting enteropathy). EpCAM-mediated cell proliferation in cancer may result from signaling (i) via regulated intramembrane proteolysis and/or (ii) the localization and association with binding partners in specialized membrane microdomains. New insight in EpCAM signaling will help to develop optimized cancer therapies and open new avenues in the field of regenerative medicine., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Endocrine release of insulin principally controls glucose homeostasis. Nutrient-induced exocytosis of insulin granules from pancreatic β-cells involves ion channels and mobilization of Ca(2+) and cyclic AMP (cAMP) signalling pathways. Whole-animal physiology, islet studies and live-β-cell imaging approaches reveal that ablation of the kinase/phosphatase anchoring protein AKAP150 impairs insulin secretion in mice. Loss of AKAP150 impacts L-type Ca(2+) currents, and attenuates cytoplasmic accumulation of Ca(2+) and cAMP in β-cells. Yet surprisingly AKAP150 null animals display improved glucose handling and heightened insulin sensitivity in skeletal muscle. More refined analyses of AKAP150 knock-in mice unable to anchor protein kinase A or protein phosphatase 2B uncover an unexpected observation that tethering of phosphatases to a seven-residue sequence of the anchoring protein is the predominant molecular event underlying these metabolic phenotypes. Thus anchored signalling events that facilitate insulin secretion and glucose homeostasis may be set by AKAP150 associated phosphatase activity.

Anthracyclines (A) and taxanes (T) are standard first-line chemotherapy agents for patients with advanced breast cancer. Platinum analogues have also shown activity in the triple-negative breast cancer (TNBC) histology, but clinical data are limited. Here we report the long-term follow-up of a phase II study on TNBC treated with a combined modality therapy, including induction with AT, cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) with concurrent radiation therapy, and a dose-dense consolidation chemotherapy (HDCT) with carboplatin (CBDCA), ifosfamide (IFX), etoposide (VP-16). Patients' median age was 44 years, with 73% premenopausal. Epirubicin 75 mg/m(2) and docetaxel 75 mg/m(2) were administered to 70 patients with TNBC: as neoadjuvant and adjuvant therapy to 12 and 58 patients, respectively. Postoperative radiation therapy, 5000 cGy, was delivered, synchronous with triweekly CMF. After radiation therapy, two courses of HDCT with CBDCA, IFX, VP-16, were given, with hematological growth factors. After a median follow-up of 81 months, all patients were evaluable for toxicity and response. Most important toxicity were grade 3 skin reaction and grade 4 hematological in 3% and 31% of patients, respectively. Pathological complete response was observed in 25% of patients receiving preoperative chemotherapy. Treatment failures were as follows: eight visceral, four contralateral breast cancer, four locoregional, and one leukemia. Five-year progression-free survival and overall survival rate were 78% and 91%, respectively. Induction chemotherapy, followed by chemoradiation therapy and HDCT, provides a prolonged disease-free period and a significant increase in overall survival in TNBC, with an acceptable toxicity profile.

Background: Netrins have been extensively studied in the developing central nervous system as pathfinding guidance cues, and more recently in non-neural tissues where they mediate cell adhesion, migration and differentiation. Netrin-4, a distant relative of Netrins 1-3, has been proposed to affect cell fate determination in developing epithelia, though receptors mediating these functions have yet to be identified., Methodology/principal Findings: Using human embryonic pancreatic cells as a model of developing epithelium, here we report that Netrin-4 is abundantly expressed in vascular endothelial cells and pancreatic ductal cells, and supports epithelial cell adhesion through integrins α2β1 and α3β1. Interestingly, we find that Netrin-4 recognition by embryonic pancreatic cells through integrins α2β1 and α3β1 promotes insulin and glucagon gene expression. In addition, full genome microarray analysis revealed that fetal pancreatic cell adhesion to Netrin-4 causes a prominent down-regulation of cyclins and up-regulation of negative regulators of the cell cycle. Consistent with these results, a number of other genes whose activities have been linked to developmental decisions and/or cellular differentiation are up-regulated., Conclusions/significance: Given the recognized function of blood vessels in epithelial tissue morphogenesis, our results provide a mechanism by which endothelial-derived Netrin-4 may function as a pro-differentiation cue for adjacent developing pancreatic cell populations expressing adhesion receptors α2β1 and α3β1 integrins.

A critical shortage of donor pancreata currently prevents the development of a universal cell-based therapy for type I diabetes. The ex vivo expansion of insulin-producing beta-cells offers a potential solution but is problematic due to the inherent tendency of these cells to transition into mesenchymal-like cells that are devoid of function. Here, we demonstrate for the first time that exposure to elements of the extracellular matrix (ECM) directly potentiates the mesenchymal transition of cultured fetal beta-cells and causes associated declines in insulin gene expression. Individual ECM constituents varied in their ability to induce such responses, with collagen-IV (C-IV) and fibronectin inducing strong responses, whereas laminin-1 had no significant effect. Mesenchymal transition and concomitant losses in insulin gene expression observed on C-IV were found to be dependent on beta(1)-integrin ligation and were augmented in the presence of hepatocyte growth factor. Importantly, selective inhibition of c-Src, c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) prior to exposure to C-IV prevented mesenchymal transition and effectively preserved insulin expression. Fetal beta-cells undergoing mesenchymal transition were found to acquire alpha(1)beta(1) expression, and ligation of this integrin then promotes declines in insulin gene expression and a marked increase in beta-cell motility. Inhibition of Src-, ERK-, or JNK-dependent signaling combined with the selective regulation of matrix exposure may ultimately facilitate the development of more effective beta-cell expansion protocols., ((c) 2010 Wiley-Liss, Inc.)

Previous studies have documented that the insulin-producing beta-cells of laboratory rodents are coupled by gap junction channels made solely of the connexin36 (Cx36) protein, and have shown that loss of this protein desynchronizes beta-cells, leading to secretory defects reminiscent of those observed in type 2 diabetes. Since human islets differ in several respects from those of laboratory rodents, we have now screened human pancreas, and islets isolated thereof, for expression of a variety of connexin genes, tested whether the cognate proteins form functional channels for islet cell exchanges, and assessed whether this expression changes with beta-cell function in islets of control and type 2 diabetics. Here, we show that (i) different connexin isoforms are differentially distributed in the exocrine and endocrine parts of the human pancreas; (ii) human islets express at the transcript level different connexin isoforms; (iii) the membrane of beta-cells harbors detectable levels of gap junctions made of Cx36; (iv) this protein is concentrated in lipid raft domains of the beta-cell membrane where it forms gap junctions; (v) Cx36 channels allow for the preferential exchange of cationic molecules between human beta-cells; (vi) the levels of Cx36 mRNA correlated with the expression of the insulin gene in the islets of both control and type 2 diabetics. The data show that Cx36 is a native protein of human pancreatic islets, which mediates the coupling of the insulin-producing beta-cells, and contributes to control beta-cell function by modulating gene expression.

Using human embryonic stem cells (hESCs), we describe a novel method for the rapid derivation and enrichment of cells that are comparable to primordial germ cells (PGCs) and Sertoli cells. The methodology described is based on modest changes to the growth conditions commonly used to expand hESCs and does not require genetic manipulation or complex three-dimensional culture. Remarkably, we have determined that simply reducing the size of cultured ESC colonies and manipulating the number of feeding cycles, results in the rapid emergence of cells that are comparable to migratory PGCs. Importantly, these cells can be monitored and purified on the basis of the expression of the chemokine receptor CXCR4. Under more stringent differentiating conditions these cells mature and upregulate the expression of specific germ cell markers. Importantly, this process is accompanied by the development of Sertoli-like support cells. Such cells normally provide trophic support and immunoprotection to developing germ cells and may have significant clinical utility in the prevention of graft rejection. The putative Sertoli-germ cell cocultures generated in this study may ultimately be developed to study and manipulate interactions and processes involved in human gametogenesis.

Objective: Vascular progenitors of bone marrow origin participate to neovascularization at sites of wound healing and transplantation. We hypothesized that the biological purpose of this bone marrow-derived vascular component is to contribute angiogenic and survival functions distinct from those provided by the local tissue-derived vasculature., Research Design and Methods and Results: To address this hypothesis, we investigated the functional impact of bone marrow-derived vascular cells on pancreatic islets engraftment using bone marrow-reconstituted Id1(+/-)Id3(-/-) mice, a model of bone marrow-derived vasculogenesis. We show that, in this model, bone marrow-derived vasculogenic cells primarily contribute to the formation of new blood vessels within islet transplants. In contrast, graft revascularization in a wild-type background occurs by tissue-derived blood vessels only. Using these distinct transplant models in which bone marrow-and tissue-derived vasculature are virtually mutually exclusive, we demonstrate that bone marrow-derived vasculogenic cells exhibit enhanced angiogenic functions and support prompt activation of islets survival pathways, which significantly impact on islets engraftment and function. Moreover, gene profiling of vascular and inflammatory cells of the grafts demonstrate that neovascularization by bone marrow-derived cells is accompanied by the activation of a genetic program uniquely tuned to downregulate harmful inflammatory responses and to promote tissue repair., Conclusions: These studies uncover the biological significance of bone marrow-derived vasculogenic cells in the response to injury during transplantation. Enhancing the contribution of bone marrow-derived vasculogenic cells to transplantation sites may help to overcome both limited angiogenic responses of the adult tissue-derived vasculature and untoward effects of inflammation on transplant engraftment.

The cross-signaling between (cell) adhesion molecules is nowadays a well-accepted phenomenon and includes orchestrated cellular changes and changes in the microenvironment. For example, Ep-CAM is an epithelial adhesion molecule that prevails in active proliferating tissue and is suppressed in a more differentiated state of the cell. E-cadherin adhesion complexes are typical for the advanced and terminal differentiated cell status. During normal proliferation, E-cadherin is not suppressed. We have demonstrated the effect of overexpression of Ep-CAM on E-cadherin, which probably affects the connection of cadherins and F-actin. Phosphatidylinositol 3-kinase (Pi3K) participates in various regulating mechanisms, for example in signaling to nuclei, vesicle transport, and cytoskeletal rearrangements. The effect of Ep-CAM on E-cadherin mediated junctions as well as the involvement of Pi3K in regulating adherens junctions, led us to investigate the potential interaction between Pi3K and Ep-CAM. Introduction of Ep-CAM in the epithelial cells caused abrogation of N-cadherin mediated cell-cell adhesion, which could be inhibited by Pi3K inhibitor LY294002. Moreover, the Pi3K subunit p85 was precipitated with Ep-CAM from cell lysates, and this complex showed kinase activity. The Pi3K activity shuttled from N-cadherin to Ep-CAM. From our results, we conclude that Ep-CAM cross signaling with N-cadherin involves Pi3K, resulting in the abrogation of the cadherin adhesion complexes in epithelial cells.

Named after the Sanskrit word netr, which means 'one who guides', the netrin family of secreted proteins provides migrational cues in the developing central nervous system. Recently, netrins have also been shown to regulate diverse processes (such as cell adhesion, motility, proliferation, differentiation and, ultimately, cell survival) in a number of non-neuronal tissues. In some cases, netrins affect these functions through non-classic netrin receptors, prompting a renewed interest in these factors in and beyond the nervous system.

The impact of extracellular matrix on insulin production needs to be understood both to optimize the derivation of functional beta-cells for transplantation and to understand mechanisms controlling islet neogenesis and glucose homeostasis. In this study, we present evidence that adhesion to some common matrix constituents has a profound impact on the transcription, secretion, and storage of insulin by human beta-cells. The integrin-dependent adhesion of fetal beta-cells to both collagen IV and vitronectin induces significant glucose-independent insulin secretion and a substantial reciprocal decline in insulin content. Collagen IV, but not vitronectin, induces comparable responses in adult beta-cells. Inhibition of extracellular signal-regulated kinase activation abrogates matrix-induced insulin secretion and effectively preserves the insulin content of adherent beta-cells. Using real-time PCR, we demonstrate that adhesion of both fetal and adult beta-cells to collagen IV and vitronectin also results in the marked suppression of insulin gene transcription. Based on these findings, we contend that integrin-dependent adhesion and signaling in response to certain matrices can have a significant negative impact on insulin production by primary human beta-cells. Such responses were not found to be associated with cell death but may precede beta-cell dedifferentiation.

We studied the effect of triphenyldioxane on phase I xenobiotic metabolism enzymes in the liver of rats and rabbits. Total cytochrome P450 content, protein concentration, and catalytic activity of CYP2B, CYP3A, and CYP2C isoforms were measured. Triphenyldioxane significantly increases specific activity of CYP2B and CYP2C in the liver of rats and rabbits, respectively. Immunoblotting analysis of microsomal enzymes in the liver of animals showed that the increase in specific activity of CYP is related to high content of apoenzymes. We showed for the first time that rats and rabbits are characterized by interspecies differences in the induction of cytochrome P450 isoforms under the influence of triphenyldioxane.

Selective expression of the human class Ib HLA molecule HLA-G in immunologically protected sites and its function in the inhibition of NK and T-cell effector functions support an important role of this molecule in immunoregulation. Here, we demonstrate that HLA-G is constitutively expressed in the endocrine compartment of the human pancreas. Surface expression of this HLA determinant in endocrine cells is regulated in response to growth and inflammatory stimuli. Furthermore, we provide evidence that HLA-G expressed in this tissue may associate with a subset of insulin-containing granules and may be shuttled to the cell surface in response to secretory stimuli. Thus, HLA-G presentation by endocrine cells may be regulated in concert with their secretory activity. These results identify the expression of a major histocompatibility complex locus with putative regulatory functions in human pancreatic islets, a finding with potentially important implications for the progression of autoimmunity as well as for the establishment of transplant tolerance to this tissue.

Collagens have been shown to influence the survival and function of cultured beta-cells; however, the utilization and function of individual collagen receptors in beta-cells is largely unknown. The integrin superfamily contains up to five collagen receptors, but we have determined that alpha(1)beta(1) is the primary receptor utilized by both fetal and adult beta-cells. Cultured beta-cells adhered to and migrated on collagen type IV (Col-IV), and these responses were mediated almost exclusively by alpha(1)beta(1). The migration of cultured beta-cells to Col-IV significantly exceeded that to other matrix components suggesting that this substrate is of unique importance for beta-cell motility. The interaction of alpha(1)beta(1) with Col-IV also resulted in significant insulin secretion at basal glucose concentrations. A subset of beta-cells in developing islets was confirmed to express alpha(1)beta(1), and this expression co-localized with Col-IV in the basal membranes of juxtaposed endothelial cells. Our findings indicate that alpha(1)beta(1) and Col-IV contribute to beta-cell functions known to be important for islet morphogenesis and glucose homeostasis.

Whether different subsets of mitochondria play distinct roles in shaping intracellular Ca2+ signals is presently unresolved. Here, we determine the role of mitochondria located beneath the plasma membrane in controlling (a) Ca2+ release from the endoplasmic reticulum (ER) and (b) capacitative Ca2+ entry. By over-expression of the dynactin subunit dynamitin, and consequent inhibition of the fission factor, dynamin-related protein (Drp-1), mitochondria were relocalised from the plasma membrane towards the nuclear periphery in HeLa cells. The impact of these changes on free calcium concentration in the cytosol ([Ca2+]c), mitochondria ([Ca2+]m) and ER ([Ca2+]ER) was then monitored with specifically-targeted aequorins. Whilst dynamitin over-expression increased the number of close contacts between the ER and mitochondria by >2.5-fold, assessed using organelle-targeted GFP variants, histamine-induced changes in organellar [Ca2+] were unaffected. By contrast, Ca2+ influx elicited significantly smaller increases in [Ca2+]c and [Ca2+]m in dynamitin-expressing than in control cells. These data suggest that the strategic localisation of a subset of mitochondria beneath the plasma membrane is required for normal Ca2+ influx, but that the transfer of Ca2+ ions between the ER and mitochondria is relatively insensitive to gross changes in the spatial relationship between these two organelles.

Circulating endothelial progenitors contribute to neovascularization at sites of injury and tumorigenesis in postnatal life. Yet, the molecular mechanisms initiating the endothelial developmental program of these precursors remain elusive. Here we provide evidence that endothelial development from progenitors circulating in human cord blood requires angiopoietins, a set of growth factors also involved in vascular branching during embryogenesis. We show that cord blood cells with the potential for endothelial development reside in a CD34(+)CD11b+ subset capable of autonomously producing and binding angiopoietins. Functionally, endogenous angiopoietin-1 regulates initial endothelial cell commitment, whereas angiopoietin-2 enhances expansion of the endothelial cell progeny. These findings suggest a role for angiopoietins as regulators of endothelial development from circulating progenitors and imply a function of angiopoietins at distinct developmental steps in postnatal angiogenesis.

While the subcellular organisation of mitochondria is likely to influence many aspects of cell physiology, its molecular control is poorly understood. Here, we have investigated the role of the retrograde motor protein complex, dynein-dynactin, in mitochondrial localisation and morphology. Disruption of dynein function, achieved in HeLa cells either by over-expressing the dynactin subunit, dynamitin (p50), or by microinjection of an anti-dynein intermediate chain antibody, resulted in (a) the redistribution of mitochondria to the nuclear periphery, and (b) the formation of long and highly branched mitochondrial structures. Suggesting that an alteration in the balance between mitochondrial fission and fusion may be involved in both of these changes, overexpression of p50 induced the translocation of the fission factor dynamin-related protein (Drp1) from mitochondrial membranes to the cytosol and microsomes. Moreover, a dominant-negative-acting form of Drp1 mimicked the effects of p50 on mitochondrial morphology, while wild-type Drp1 almost completely restored normal mitochondrial distribution in p50 over-expressing cells. Thus, the dynein/dynactin complex plays an unexpected role in the regulation of mitochondrial morphology in living cells, by controlling the recruitment of Drp1 to these organelles.

The cell adhesion molecule L1 has been implicated in a variety of motile processes, including neurite extension, cerebellar cell migration, extravasation, and metastasis. Homophilic or heterophilic L1 binding and concomitant signaling have been shown to promote cell motility in the short term. In this report, L1 is also shown to induce and maintain a motile and invasive phenotype by promoting gene transcription. In the presence of serum or platelet-derived growth factor, L1 promotes heightened and sustained activation of the extracellular signal-regulated kinase pathway. Activation of this pathway then induces the expression of motility- and invasion-associated gene products, including the beta(3)-integrin subunit, small GTPases, and the cysteine proteases cathepsin-L and -B. Induction of integrin alpha(v)beta(3) and rac-1 is shown to contribute directly to L1-dependent haptotaxis, whereas induction of cathepsins-L and -B promotes matrix invasion. This study provides a novel translational mechanism to account for the association between L1 expression and motile processes involved in metastasis and development.

The role of individual integrins in human beta-cell development and function is largely unknown. This study describes the contribution of alpha(v)-integrins to human beta-cell adhesion, spreading, and motility. Developmental differences in alpha(v)-integrin utilization are addressed by comparing the responses of adult and fetal beta-cells, and vitronectin is used as a substrate based on its unique pattern of expression in the developing pancreas. Fetal and adult beta-cells attached equally to vitronectin and integrin alpha(v)beta(5) was found to support the adhesion of both mature and immature beta-cell populations. Fetal beta-cells were also observed to spread and migrate on vitronectin, and integrin alpha(v)beta(1) was found to be essential for these responses. In contrast to their fetal counterparts, adult beta-cells failed to either spread or migrate and this deficit was associated with a marked down-regulation of alpha(v)beta(1) expression in adult islet preparations. The integrin alpha(v)beta(3) was not found to support significant beta-cell attachment or migration. Based on our findings, we conclude that integrins alpha(v)beta(5) and alpha(v)beta(1) are important mediators of human beta-cell adhesion and motility, respectively. By supporting fetal beta-cell migration, alpha(v)beta(1) could play an important role in early motile processes required for islet neogenesis.

Netrins, axon guidance cues in the CNS, have also been detected in epithelial tissues. In this study, using the embryonic pancreas as a model system, we show that Netrin-1 is expressed in a discrete population of epithelial cells, localizes to basal membranes, and specifically associates with elements of the extracellular matrix. We demonstrate that alpha6beta4 integrin mediates pancreatic epithelial cell adhesion to Netrin-1, whereas recruitment of alpha6beta4 and alpha3beta1 regulate the migration of CK19+/PDX1+ putative pancreatic progenitors on Netrin-1. These results provide evidence for the activation of epithelial cell adhesion and migration by a neural chemoattractant, and identify Netrin-1/integrin interactions as adhesive/guidance cues for epithelial cells.

Studies using adult human islets and mouse embryonic stem cells have suggested that the neurepithelial precursor cell marker nestin also identifies and can be used to purify beta-cell precursors. To determine whether nestin can be used to identify beta-cell progenitors in the developing human pancreas, we characterized nestin expression from 12 to 24 gestational weeks, purified nestin+ cells using an enhancer/promoter-driven selection plasmid, and determined whether nestin+ cells can differentiate into beta-cells. Nestin was visualized in the platelet endothelial cell adhesion molecule and alpha smooth muscle actin-positive blood vessels and colocalized with vimentin in the interstitium. Nestin was not observed in pan cytokeratin (pCK)-positive ductal epithelium or insulin cells. Purified nestin+ cells also coexpressed vimentin and lacked pCK immunoreactivity. Purified adult and fetal pancreatic fibroblasts also expressed nestin. The nestin enhancer/promoter used in the selection plasmid was sufficient to drive reporter gene expression, green fluorescent protein, in human fetal pancreatic tissue. Exposure of selected nestin+ cells to nicotinamide, hepatocyte growth factor/scatter factor, betacellulin, activin A, or exendin-4 failed to induce pancreatic and duodenal homeobox gene-1 or insulin message as determined by RT-PCR. Transplantation of nestin+ cells and fetal pancreatic fibroblasts into athymic mice also failed to result in the development of beta-cells, whereas nestin- fetal pancreatic epithelial cells gave rise to functional insulin-secreting beta-cells. We conclude that nestin is not a specific marker of beta-cell precursors in the developing human pancreas.

Connexin channels clustered at gap junctions are obligatory attributes of all macroscopic endocrine and exocrine glands investigated so far and also connect most types of cells which produce secretory products in other tissues. Increasing evidence indicates that connexins, and the cell-to-cell communications that these proteins permit, contribute to control the growth of secretory cells, their expression of specific genes and their differentiated function, including their characteristic ability to biosynthetize and release secretory products in a regulated manner. Since the previous reviews which have been published on this topic, several lines of evidence have been added in support of multiple regulatory roles of gland connexins. Here, we review this novel evidence, point to the many questions which are still open and discuss some interesting perspectives of the field.

Cell-cell and cell-matrix interactions play a critical role in tissue morphogenesis and in homeostasis of adult tissues. The integrin family of adhesion receptors regulates cellular interactions with the extracellular matrix, which provides three-dimensional information for tissue organization. It is currently thought that pancreatic islet cells develop from undifferentiated progenitors residing within the ductal epithelium of the fetal pancreas. This process involves cell budding from the duct, migration into the surrounding mesenchyme, differentiation, and clustering into the highly organized islet of Langerhans. Here we report that alpha(v)beta(3) and alpha(v)beta(5), two integrins known to coordinate epithelial cell adhesion and movement, are expressed in pancreatic ductal cells and clusters of undifferentiated cells emerging from the ductal epithelium. We show that expression and function of alpha(v)beta(3) and alpha(v)beta(5) integrins are developmentally regulated during pancreatic islet ontogeny, and mediate adhesion and migration of putative endocrine progenitor cells both in vitro and in vivo in a model of pancreatic islet development. Moreover, we demonstrate the expression of fibronectin and collagen IV in the basal membrane of pancreatic ducts and of cell clusters budding from the ductal epithelium. Conversely, expression of vitronectin marks a population of epithelial cells adjacent to, or emerging from, pancreatic ducts. Thus, these data provide the first evidence for the contribution of integrins alpha(v)beta(3) and alpha(v)beta(5) and their ligands to morphogenetic events in the human endocrine pancreas.

Laminin-5 (Ln-5) is an extracellular matrix substrate for cell adhesion and migration, which is found in many epithelial basement membranes. Mechanisms eliciting migration on Ln-5 need to be elucidated because of their relevance to tissue remodeling and cancer metastasis. We showed that exogenous addition of activated matrix metalloprotease (MMP) 2 stimulates migration onto Ln-5 in breast epithelial cells via cleavage of the gamma2 subunit. To investigate the biological scope of this proteolytic mechanism, we tested a panel of cells, including colon and breast carcinomas, hepatomas, and immortalized hepatocytes, selected because they migrated or scattered constitutively in the presence of Ln-5. We found that constitutive migration was inhibited by BB94 or TIMPs, known inhibitors of MMPs. Limited profiling by gelatin zymography and Western blotting indicated that the ability to constitutively migrate on Ln-5 correlated with expression of plasma membrane bound MT1-MMP metalloprotease, rather than secretion of MMP2, since MMP2 was not produced by three cell lines (one breast and two colon carcinomas) that constitutively migrated on Ln-5. Moreover, migration on Ln-5 was reduced by MT1-MMP antisense oligonucleotides both in MMP2+ and MMP2- cell lines. MT1-MMP directly cleaved Ln-5, with a pattern similar to that of MMP2. The hemopexin-like domain of MMP2, which interferes with MMP2 activation, reduced Ln-5 migration in MT1-MMP+, MMP2+ cells, but not in MT1-MMP+, MMP2- cells. These results suggest a model whereby expression of MT1-MMP is the primary trigger for migration over Ln-5, whereas MMP2, which is activated by MT1-MMP, may play an ancillary role, perhaps by amplifying the MT1-MMP effects. Codistribution of MT1-MMP with Ln-5 in colon and breast cancer tissue specimens suggested a role for this mechanism in invasion. Thus, Ln-5 cleavage by MMPs may be a widespread mechanism that triggers migration in cells contacting epithelial basement membranes.

There is growing interest in using human umbilical cord blood (CB) for allogeneic bone marrow transplantation (BMT), particularly in children. Thus, CB has been identified as a rich source of hematopoietic progenitors of the erythroid, myeloid, and B-cell lineages. Whether CB blood cells engrafting in the BM space also comprise T-cell progenitors capable of trafficking to the thymus and reconstituting a functional thymopoiesis in young recipients is presently unknown. Here, we show that CB progenitors, engrafted in the BM of immunodeficient mice, sustain human thymopoiesis by generating circulating T-cell progenitors capable of homing to and developing within a human thymic graft. Surprisingly, development of CB stem cells in this in vivo model extended to elements of the endothelial cell lineage, which contributed to the revascularization of transplants and wound healing. These results demonstrate that human CB stem cell transplantation can reconstitute thymic-dependent T-cell lymphopoiesis and show a novel role of CB-derived hematopoietic stem cells in angiogenesis.

Ex vivo expansion of human beta-cells is an important step toward the development of cell-based insulin delivery systems in type 1 diabetes. Here, we report that human pancreatic endocrine cells can be expanded through 15 cell doublings in vitro for an estimated total 30,000-fold increase in cell number. We believe that the cells resulting from these cultures are of beta-cell origin, since they uniformly express the transcription factor PDX-1 (STF-1, IDX-1, IPF-1), which is initially seen only in cells positive for insulin and negative for the ductal cell marker cytokeratin (CK)-19. To rule out the possibility that PDX-1 expression might be induced by the culture conditions used here, cells from isolated human pancreatic ducts were cultured under the same conditions as the islet cells. Cells in these cultures expressed CK-19 but not PDX-1. Although the expanded beta-cells continued to express PDX-1, insulin expression was lost over time. Whether reexpression of islet-specific genes in vitro is essential for successful cell transplantation remains to be determined.

We have studied the factors that influence the efficiency of infection of human fetal and adult pancreatic endocrine cells with adenovirus, murine retrovirus, and lentivirus vectors all expressing the green fluorescent protein (Ad-GFP, MLV-GFP, and Lenti-GFP, respectively). Adenoviral but not retroviral vectors efficiently infected intact pancreatic islets and fetal islet-like cell clusters (ICCs) in suspension. When islets and ICCs were plated in monolayer culture, infection efficiency with all three viral vectors increased. Ad-GFP infected 90-95% of the cells, whereas infection with MLV-GFP and Lenti-GFP increased only slightly. Both exposure to hepatocyte growth factor/scatter factor (HGF/SF) and dispersion of the cells by removal from the culture dish and replating had substantial positive effects on the efficiency of infection with retroviral vectors. Studies of virus entry and cell replication revealed that cell dispersion and stimulation by HGF/SF may be acting through both mechanisms to increase the efficiency of retrovirus-mediated gene transfer. Although HGF/SF and cell dispersion increased the efficiency of infection with MLV-GFP, only rare cells with weak staining for insulin were infected, whereas approximately 25% of beta-cells were infected with Lenti-GFP. We conclude that adenovirus is the most potent vector for ex vivo overexpression of foreign genes in adult endocrine pancreatic cells and is the best vector for applications where high-level but transient expression is desired. Under the optimal conditions of cell dispersion plus HGF/SF, infection with MLV and lentiviral vectors is reasonably efficient and stable, but only lentiviral vectors efficiently infect pancreatic beta-cells.

We examined the role of Laminin-5 (Ln-5) an extracellular matrix component of breast gland basement membrane, in supporting migration of normal (HUMEC), immortalized (MCF-10A), and malignant breast epithelial cells that exhibit different degrees of metastatic potential (MDA-MB-435>MDA-MB-231>MCF-7). HUMEC, MCF-10A, and MCF-7 cells all adhered to purified Ln-5 through the alpha3beta1 integrin receptor in adhesion assays. However, HUMEC and MCF-10A cells remained statically adherent, while MCF-7 cells migrated on Ln-5 in Transwell and colloidal gold displacement assays. Anti-alpha3 integrin antibodies blocked migration of MCF-7 cells on Ln-5. MDA-MB-231 and MDA-MB-435 cells bound and migrated on Ln-5 through a beta1 integrin receptor that is insensitive to antibodies that block the function of alpha1, alpha2, alpha3, alpha4, alpha5, alpha6, and alphaV integrin subunits. Migration of all cell types tested was blocked by CM6, a monoclonal antibody directed to a cell adhesion site on the alpha3 chain of Ln-5. Thus, Ln-5 may play an important role in regulating adhesion and migration in normal and transformed breast epithelium. Our results indicate that the type of integrin utilized by breast cells to interact with Ln-5, as well as its functional state, may determine whether cells will be statically adherent or migratory on Ln-5.